The safe and reliable operation of a railroad system is dependent upon the integrity of the rolling mechanisms of the vehicles traveling over the rails. For example, it is important to monitor a condition of train wheel bearings to determine if a degree of wear on the bearing indicates that the bearings need to be inspected and repaired or replaced. Worn or damaged bearings increase the rolling friction of the axle thereby increasing the power required to pull the train. In addition, worn or damaged bearings may cause excessive wear to the train axle and, in the case of failure of the bearing, may even cause the axle to lock up, preventing rotation of the wheel, resulting in a potential fire hazard due to the heat build up and potential sparking caused by friction of the locked wheel scraping along the rail.
Bearing temperatures may be directly monitored using rail car mounted temperature sensors, such as thermocouples, disposed near the bearings. However, such techniques having proven to be unreliable and/or relatively costly to operate and maintain. One way of indirectly monitoring the a condition train wheel bearings is to sense a temperature of the wheel bearing indirectly through a bearing box surrounding the wheel bearing on a rail car of a train. For example, infrared radiation (IR) sensors have been mounted along a rail to detect IR energy emitted by an outer wheel bearing and indicative of a temperature of the wheel bearing, as the rail car passes the IR sensor. However, such a system may be limited to a certain rail car wheel configuration that allows an unimpeded sensing path from the sensor to the bearing box, which may not be achievable for all rail car wheel configurations. Furthermore, inner wheel bearings used on some rail cars and locomotives have proven difficult to monitor due to sensing paths being blocked by suspension components and the differences among inner wheel bearing arrangements. In addition, the presence of IR sources near an inner bearing being monitored, such as gear boxes or suspension springs, and the effects of lateral movement of the axle bringing other IR sources into a sensing path, such as during wheel hunting, may result in erroneous IR readings for the bearing. Other IR sources which may interfere with a temperature measurement of a train wheel bearing may include hot lubricant leakage, sun reflections, differential heating on different sides of a train, sparks from skidding wheels, and brake hardware, such as brake disks. Accordingly, an improved system and method for sensing a temperature of train wheel bearings is desired.